Lubricant for marine diesel engines



United States Patent 3,216,937 LUBRICANT FOR MARINE DIESEL ENGINESArnold J. Morway, Clark, and Fredrick L. Jonach, Short Hills, N..I.,assignors to Esso Research and Engineering Company, a corporation ofDelaware N0 Drawing. Filed Dec. 7, 1962, Ser. No. 242,930 2 Claims. (Cl.252-39) This invention relates to lubricants. Particularly, theinvention relates to lubricating oil compositions, having good antiwearproperties, comprising mineral oil and alkaline earth metal salts ofacetic acid and dicarboxylic acid.

While generally useful as lubricants for a variety of purposes,lubricants can be made according to the invention which are particularlyeflective for cylinder lubrication of marine diesel engines. Althoughmarine diesel engines have become wide spread in their use, in theseengines there has always been a serious wear problem with regard to thepiston, the piston rings and the surface of the cylinder liner.

In lubricating these diesel engines, a fluid or semi-fluid lubricant issprayed or forced directly onto the cylinder upon each stroke of thepiston by means of a centralized forcefeed lubrication system. Thelubricant is to a large extent consumed during each stroke of thepiston, thereby requiring continuous application of the lubricant.

in order to be suitable for such lubrication use, the lubricant shouldhave a fluid or semi-fluid consistency. This is desired in order thatthe lubricant may be readily pumped through the aforementioned forcedlubrication systems normally associated with marine diesel engines andwill spread or Wet the piston sufliciently during each stroke to achievean overall coating on the piston surface. As indicated above, anotherrequirement of such lubricants is that they have good antiwearproperties. Because of the giant size of the pistons and cylinders usedin such engines (e.g. piston and cylinder diameters of about 36 inchesare common), wear is a serious problem. Once the cylinder liner has wornmore than about 0.6% of its diameter, it is necessary that it bereplaced. In a typical marine engine of 8 to 16 cylinders suchreplacement cost may run in the order of several thousand dollars percylinder. Wear of the piston and rings is also an expensive problem. Thelubricant should also be storage stable, even when subject to longperiods of vibration as occurs during storage in a ships engine room.

Lubricants for such marine diesel lubrication, which met the aboverequirements, have been made by thickening mineral lubricating oil withmixed calcium salts of acetic acid and an intermediate molecular weightfatty acid, e.g. C to C or C fatty acids. It has now been found thatmarine diesel lubricants superior in several respects to those made fromthe intermediate molecular weight fatty acids and acetic acid, can beprepared by using dicarboxylic acid in place of part or all of theintermediate molecular weight fatty acid. By the use of the dicarboxylicacid, marine diesel lubricants can be prepared which are superior tosaid intermediate fatty acid type lubricant by having a reduced tendencyto gel under hot conditions. Thus, in some engines operating at veryhigh temperatures, gelling of the lubricant will interfere with thespreading of the lubricant onto the piston and cylinder, and will alsointerfere with pumping the lubricant through narrow diameter feed lines.In addition, in general the use of dicarboxylic acid results in a betterice dispersion of calicum acetate, greater fluidity, and improvedspreadability than is obtained by use of said aforementionedmonocarboxylic acids.

The dicarboxylic acids operable in the invention include those of theformula:

HOOCRCOOH composition is preferably calcium since it results in theproduction of stable lubricants having load carrying and antiwearcharacteristics even without the use of conventional extreme pressureand stabilizing agents. The other alkaline earth metals such as barium,strontium and magnesium can be used, but are not as good as calcium inthese respects.

The mixture of alkaline earth metal salts of the invention can beprepared by neutralization of acetic acid or acetic anhydride anddicarboxylic acid with suitable bases, particularly hydrated lime. Theneutralization step can be carried out in situ in the oil menstruum towhich the mixture of salts is to be applied in actual use, usuallyfollowed by dehydration by heating to about 250 to about 350 F. untilthe salt mixture is substantially anhydrous, i.e. there is no free orunbound water present. It is generally desirable to use a slight excessof base, e.g. lime, in order to form a slightly alkaline final product,e.g. 0.05 to 0.2 wt. percent alkalinity as measured in terms of NaOH.This alkalinity helps to neutralize corrosive acids formed bydegradation of the lubricant during use and also imparts greaterstability of the lubricant. Also the alkalinity helps to neutralizecorrosive sulfur-containing acids that may form upon combustion of highsulfur content fuel oil.

The mixture of alkaline earth metal salts of the invention can also beprepared by first forming at least a portion of the salt of thedicarboxylic acid in oil, then forming the acetate salt byneutralization in the presence of dicarboxylic acid salt, then heatingunder substantially dehydration conditions. This method is believed toresult in a more stable lubricant since dicarboxylic acid salt isbelieved to limit the crystal growth of the acetate salt particles whichare subsequently formed by the neutralization of the acetic acid withmetal base. Also, when using lime, it is generally desirable to carryout the bulk of the neutralization with insufficient lime present sothat the excess acid will react with any carbonates that may be presentin commercial lime, then adding a small amount of additional lime tocompletely neutralize the acids and preferably to also form an alkalineproduct.

The mixed. salt lubricants of the invention can be prepared by using 1to 100, preferably 5 to 40, molar hydrogen equivalents of acetic acid oracetic anhydride per molar hydrogen equivalent of dicarboxylic acid. Forlubricants designed for marine diesel lubrication, good results areobtained by using a ratio of about 5 to 15 molar hydrogen equivalents ofthe acetic acid or its anhydride per molar hydrogen equivalent ofdicarboxylic acid.

The finished lubricant will generally be a fluid or semifluid comprisinga major amount of lubricating oil and about 3 to 20, preferably 5 to 12wt. percent of the mixed ing large scale manufacture, concentrates of 20to 45 wt.

percent of the mixed salts in oil can be made by the in situ technique,after which the concentrate is diluted with additional oil to form thefinished lubricant. This dilution is readily made by adding theadditional oil and mixing. Both the concentrate and finished lubricantcan be homogenized in a Morehouse mill, Charlotte mill, Gaulinhomogenizer, etc. If enough of the mixed salt is used in the oil, a softsolid grease is obtained. However, these greases do not seem to havevery good structural stability. As a result, the mixed salt compositionof the invention is preferably used in the form of fluid or semi-fluidlubricant.

Mineral oil is the preferred lubricating oil, although various syntheticoils such as polysilicone, silanes, esters, Ucons, etc. may be used forspecial uses.

Various additives can be added to the finished lubricant in amounts of0.1 to 10.0 wt. percent, based on the weight of the finished lubricant.Among additives that can be added are corrosion inhibitors such assodium nitrite, lanolin, wool grease. stearin; antioxidants such asphenyl-alpha-naphthylamine; extreme pressure agents; dyes; etc.

The invention will be further understood by references to the followingexamples which include preferred embodirnents of the invention.

EXAMPLE I (All parts by weight) 9.45 parts of hydrated lime and 69.3parts of a mineral lubricating oil having a viscosity of 80 SUS at 210F. were added to a steam jacketed grease kettle and intimately mixed toa smooth slurry. Then 1.14 parts of LIZ-dodecanedioic acid was added,with mixing. Mixing was continued for /2 hour, following which 16 partsof glacial acetic acid was slowly added while mixing over a period ofanother /2 hour. All of this mixing was carried out by circulating thegrease from the grease kettle through a Charlotte mill having an 0.005"clearance. After the composition has been thus thoroughly mixed, 2.66parts of dodecanedioic acid were added and the temperature of themixture was raised by heating to 205 P. Then 1.05 parts of additionallime was added to give a free alkalinity content of 0.1 wt. percentdetermined as NaOH. All during the preceding period, the grease wascontinuously circulated through said Charlotte mill. The temperature ofthe grease was next raised to about 310 F. without milling. Thetemperature at 310 F. was held for 30 minutes, after which thegrease-was cooled by passing water through the kettle jacket. Uponcooling the grease to 200 F., 0.4 part of phenyl-alpha-naphthylamine wasadded as an oxidation inhibitor. The grease was further cooled to 100 F.where it was again milled by passage through the Charlotte mill. Theresulting product was an excellent smooth grease having a consistency ofa very viscous fluid. 1 part of this grease was then mixed with 3 partsof additional mineral lubricating oil of 80 SUS viscosity at 210 F. Thediluted product was then passed through a Charlotte mill having aclearance of 0.003 after which the product was filtered through a 60mesh screen and then packaged.

COMPARISON LUBRICANT For comparison, a marine diesel cylinder lubricantwas prepared by coneutralizing acetic acid and Wecoline AAC acid withlime in a mineral lubricating oil. A mole ratio of 12 molar hydrogenequivalent proportions of acetic acid per molar hydrogen equivalent ofWecoline AAC acid had been found to give the best overall results in amarine diesel cylinder lubricant. Wecoline AAC acid is a commercial acidderived from coconut oil and consisting of about 46 wt. percent capricacid, about 28 wt. percent caprylic acid and about 26 wt. percent lauric4 I acid. The comparison composition was dehydrated at a temperature ofabout 320 F. The product was homogenized by passage through a Morehousemill.

The products prepared above and their properties are summarized in thefollowing table:

Vis./210 F. SUS 78 1 Base No. ASTM D664 mm.

KOH/gm Centrifuge Test, Percent Sedi- 0.65 0.8.

ment, 1,500 r.p.m.4 hours. Hote Plate Spread Test 450 F. SpreadsCoagulates. Oven Test, 4 hours at 350 F Does not gel. Gels. 4-Ball WearTest, scar diam., .23 mm- .30 mm.

mm. 1 hr.-1,800 r.p.m.10 kg. Load. Mesh Screen Test Readily passesPasses through.

through. Manzell Lubrication Test days. 18 days. Thermal Stability Test:

C Fluid No gel. C Fluid Gel.

The products of Example I gave a very low wear scar diameter of 0.23 mm.in the 4-Ball Wear Test as compared to a scar diameter of 0.30 mm. forthe comparison lubricant.

The Manzell Lubricator test of Table I is carried out by passing thelubricant under test through a Manzell Lubricator at the rate of 2quarts of lubricant a day. The Manzell Lubricator includes a sight-glassfilled with an aqueous solution containing 50 wt. percent of a calciumnitrate tetrahydrate as the sight-glass-fluid. These lubricators arewidely used in conjunction with marine diesel engines. The lubricatorpermits visual observation of the rate of flow of the lubricant which isforced into the bottom of the sight-glass and then floats up through thehigher density sight-glass fluid to an upper line from where it is thenforced to the cylinder being lubricated. The product of Example I wentfor 120 days without fogging the sight-glass. On the other hand, thecomparison lubricant went for only 18 days before the sight-glass hadbecome sufficiently fogged so as to require disassembling and cleaning.

The Thermal Stability test was carried out by filling an ASTM pour pointjar full with the lubricant to be tested. The test lubricant was heatedfor four hours and is then cooled for 45 minutes. The jar is thenexamined to see if the lubricant has gelled. It is seen that at the 190C. heating level, that the comparison lubricant had gelled while theproduct of Example I had not. This gelling or lack of gelling is used asan indication of the spreading ability of the lubricant when it hits thehot cylinder it is being used to lubricate. For example, a cylinder at atemperature of 190 C., when hit by the comparison lubricant of Table Iwould cause the lubricant to gel so as to interfere with thespreadability of the lubricant along the cylinder walls. On the otherhand, the product of Example I will not form a gel at this temperatureand as a result will remain fluid so that it can rapidly spread alongthe cylinder to more evenly wet the cylinder with the lubricant.

The Hot Plate Spread Test is carried out by simply allowing drops of thelubricant to fall on a hot iron surface at 450 F. and observing whetheror not the lubricant spreads or gels.

The data of the table shows that the product of the invention resultedin a lubricant which was more fluid,

more stable against sedimentation as measured by the Centrifuge Test,did not gel on a hot iron surface at 450 F. or in the Thermal StabilityTest, gave lower wear and was slower to foul the Manzell Lubricator thanthe comparison lubricant.

The table also demonstrates the lower thickening power of thedicarboxylic acid salt as compared to the monocarboxylic acid Wecolinesalt. This represents a major advantage for many types of uses, since itpermits the incorporation of large amounts of calcium acetate salt intooil with relatively little thickening. Thus, the excellent anti-wearproperties imparted by calcium acetate can be incorporated into oil toform more fluid lubricants than could generally be heretofore obtained.

What is claimed is:

1. A fluid marine diesel cylinder lubricant having a reduced tendency togel at high temperatures consisting essentially of a major proportion ofmineral lubricating oil and about 5 to 12 wt. percent of calcium salt ofacetic acid and C to C unsubstituted saturated aliphatic dicarboxylicacid in a molar hydrogen equivalent ratio of 6 said acetic acid to saiddicarboxylic acid of about 5:1 to 15:1.

2. A fluid marine diesel cylinder lubricant having a reduced tendency togel at elevated temperatures consisting essentially of a majorproportion of mineral lubricating oil and about 5 to 12 wt. percent ofcalcium salt of acetic acid and dodecanedioic acid in a molar hydrogenequivalent ratio of said acetic acid to said dicarboxylic acid of about5:1 to 15:1.

References Cited by the Examiner UNITED STATES PATENTS 2,363,514 11/44Farrington et al. 25240.7 2,699,428 1/55 Lux et a1. 25239 2,846,392 8/58Morway et a1 25239 X 2,859,179 11/58 Lux et a1. 25239 X 2,976,242 3/61Morway 25239 X 3,002,926 10/61 Bergen 252-40.7 X 3,071,547 1/63 Morway25239 DAN TEL E. WYMAN, Primary Examiner.

1. A FLUID MARINE DIESEL CYLINDER LUBRICANT HAVING A REDUCED TENDENCY TOGEL AT HIGH TEMPERATURES CONSISTING ESSENTIALLY OF A MAJOR PROPORTION OFMINERAL LUBRICATING OIL AND ABOUT 5 TO 12 WT. PERCENT OF CALCIUM SALT OFACETIC ACID AND C10 TO C14 UNSUBSTITUTED SATURATED ALIPHATICDICARBOXYLIC ACID IN A MOLAR HYDROGEN EQUIVALENT RATIO OF SAID ACETICACID TO SAID DICARBOXYLIC ACID OF ABOUT 5:1 TO 15:1.